I'm not sure what you mean re the power plug, but that router should work fine, connected as you say to the Ethernet feed from the Openreach modem.
However, there are two sort of "Engineer install". The standard one is that the engineer's job is to get the modem (and line) working properly. The "Managed install" used by BT Retail (and a couple of others I think) the engineer also connects up the router and makes sure the internet connection through the ISP is made. I don't know which Zen provides.
In any case, it's an Ethernet cable from the modem to your router, and depending on the ISP you either enter your login username and password or you let TR-069 do its stuff.
My broadband basic info/help site - www.robertos.me.uk
| Domains,site and mail hosting - Tsohost
Connection - Plusnet
UnLim Fibre (FTTC). Sync ~ 56.6/14.1Mbps @ 600m. - BQM
"Where talent is a dwarf, self-esteem is a giant."
- Jean-Antoine Petit-Senn.
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Edited by RobertoS (Thu 21-Aug-14 21:43:06)